Waterproofed fabric and method of producing it



Patented Nov. 20, 1951 WATERPROOFED FABRIC or RODUQ JN I7 David N. Beauchamp, Venice, =Calif.,.,assignor to Wingfoot Corporation, Akr0n, ;Q1 io, acorpo gae o D aw re NfoDrawing. Application October 31, 1946,

l This invention relates .to compositions useful in film formation, and for coatingitextilefabrics, and to new coated fabrics capable of transmitting water vapor. More specifically, the invention re..- lates to water-impermeable, water-vaporepermeable fabrics having a coating of polydiene rubber. The application of water-proof coatings to cloth is well known and many satisfactory .methods have been devised for effecting this objective. However, when'the cloth, thus treated is-to be used for garments-such as raincoats, these coating compositions arenot wholly satisfactory because they do not transmit the water vapor resulting from body perspiration. As a result, the comfort of the wearer is greatly impaired. To overcome this objection, light-weight'f-abrics of closely woven fibers are widely used for the manufacture of so-called rain-proof garments because they do transmit-water vapor, butthese fabrics are not sufiiciently water-proof to prevent the penetration of liquid water when subjected to rainfall for long periods of time or to substantial hydrostatic pressure. Rain-proof garments have also been made by treating woven fabrics :with organic silicon-compounds, such as the silanes, or othercompounds which render the fabric hydrophobic, or water-repellent, but these also do not withhold water under the hydrostatic pressures experienced in normal usage.

The primary purpose of this invention-is to provide new water-proof fabrics capable of exeluding liquid water under substantial hydrostatic pressures and yet which are quite pervious to gases, and especially .to water vapor. A further purpose is to providewater-proof ,compositions useful in the preparation of films and coatings, capable of transmitting water vapor while being impervious to liquidwater.

In accordance with this invention films are prepared, or woven fabrics are coated, with a specially compounded polymerized diene synthetic rubber. Useful rubbers of this type are polyisoprene, polymerized butadiene-lgb polymers of other conjugated dioleiinic hydrocarbons and the polymers of chlorine-substituted,diolfinic hydrocarbons, such as 2-chloro-butadiene- 1,3. The coating of cloth with polydiene rubhers is not new and such practice will not, of itself, yield a water .vaporlpervious fabric.

In order to secure thedesired result, thecoating compositions are specially compounded with large proportions of a hydrophilic diatomaceous earth or other similar naturally. occurring fossil remains of microscopic-marine animals, including diatoms and other-photophyta. These minerals are known as .infusorial earth. dietemaceoue silica, and .kieselgunrandare availa l in va ious statesof refinement under the trade names o 'sil oecel', iCeli-te," and f supe iinss, ,Eor the p rpose of this. patent applicati n .allooi these minerals in their natural state and in purifi form are intended to be. included within the generic expression ,-fidiatomaceous ear th.-.

.The different minerals .vary substantially :in their densities and-forthe nurpose.o-f,.d fininath invention it has been ionndrthat the volumeratios of the ,diatomaceous ,earth are more ,significani than the-weightratios. A usefulcomposition can be-preparedbycompoimdingthe olydienexrubber with at ieasbtwovolumes of diatomaceousearth. the volume being based on the csovealled. iapparent .density measured by pouring .the p ment= into ,a graduatelorother.volume measurin device. The pref erred compositions .Will c ntain fromrthlteeto rive. volumes oild atomaeeous arth. If-morethan six ,volumeslof th spi mentare used. m ny compositions become 'tposrigid .oryisemn for ready vapplication to cloth especially when the.latex.techniquen er in ii ese ibedo snsesl- A preferred method-fol.- pr par n thelnew geinpositions .ai volves ethe .nse :of th latex as it i obtainedhyi.the..=BmuliQIl poly rization .ofthe diene. :Thelatexsdprepared is usuallyanaquee oussusnension ;0f-5fi.I1Q1Yr$lWld6-. sqlidnarticlesni polymer, theemulsion:beingusually. stabilizediby the. presence. ofv soapsor, othenwettiligsa n The latex Ana-y ,be used -;di1".ectly; ;in thisrform, -9 sit. maybe concentrated by, creaminaagglomeratipg or centrifuging many-mannerewelleknown,to-the art. .The solid rubbencontent ,of -;these aqueous suspensionsimayyary between .30 and.;55 percent solids. zlnithe practice ofsthis invention-the poly:- dienerlatices areieompounded with antioigidants. accelerators, plasticizers .and coloring agents in theimannerw'ellknoyvn to the art. Suitableantioxidants for ,use in the polydiene rubbers are phenyl-betaenaphthylamine, :.-butyraldehyde=aniline,.derivativeandniebeta-naphthyl-sparaephene ylene :diamine. :The ,-conventional accelerators used thesecompositions are 'hexamethylene ammonium hexamethylenedithio .carbamate,

3 be prepared by compounding solid polydiene rubber on a rubber mill with theconventional antioxidants, plasticizers, and accelerators, as above described. The rubber so compounded is then dissolved or dispersed in organic solvents, such as benzene, toluene, methyl ethyl ketone, ethylene, dichloride, chlorobenzene, high naphthenic petroleum fractions. Although sometimes regarded as true solutions, the mixtures of organic solvents and polydiene rubbers are believed to be colloidal dispersions of rubber particles in the organic liquids in which the organic liquid is the exterior phase, or dispersion medium, just as the water is the exterior'phase ofa'latex, or

aqueous dispersion. The dispersion of the polydlene rubber in the solvent is effected by adding the compounded rubber to the solvent in a dough mixer or other conventional mixing device. Sufficient solvent is added to make a thin cement and the desired amount of the diatomaceous earth is thereafter added to yield a thick cement which can be fabricated by the same methods useful in the fabrication of the compounded latex, by painting, spraying, calendering, spreading or other methods well known to the art.

The principal use of the above-described coating compositions is in the coating of fabrics which may be woven or knitted of animal fiber, such as wool, silk, fur and hair, vegetable fibre, such as cotton, linen and hemp, mineral fibre, suchas glass and asbestos, and synthetic fibre, such as rayon or nylon. Matted fabrics, such as felt and paper may also be coated. The apparatus and method used for impregnating or coating the fabrics are well known and are not a part of this invention.

The preferred method of applying the coatings involves the spreading technique, in which cloth is drawn tightly over a series of rolls or other devices and the compounded latex or solvent dispersion is applied using a doctor blade or other straight edge to control the thickness. The blade may be set up perpendicularly to the fabric or at an angle so as to force the coating composition into the interstices. Frequently it is desirable to apply several successive layers, allowing each to dry wholly or partially before applying the next layer. The first layer is sometimes applied with the spreader knife set at zero clear- -ance so that only the interstices are filled on the first application, the desired covering layers being put on subsequently by separate spreading operations. After each coating, or after several coatings have been applied, the composition is dried, by heating, if necessary, to remove the water or other liquid present in the rubber dispersion. The dried coating is then vulcanized by heating the coated fabric to the vulcanization temperature of the particular compound.

The new compositions may also be used without the fabric base in the form of films. Such films will have the same properties of waterimperviousness and water-vapor-permeability as the cloth laminates, but generally do not have the tensile and fiexural strengths; They are, however, useful forthe fabrication of items not intended to be subjected to severe stress.

The coated fabrics and the films may be used in the fabrication of coats, gloves, boots and shoes, and other wearing apparel as well as tents, sleeping bags, hospital sheeting, bandage wrappers, tarpaulins, furniture coverings or other structures adapted for enclosing or contacting the human body.

....The. water vapor perviousness. of the coated fabrics may be tested by any of several standard methods. In the examples below the coated fabrics were tested by cementing a sample of the fabric to the top edge of a glass Petri dish containing water, the level of which is 2.3: .05 cm. below the fabric, and measuring the water evaporated during a predetermined period of time. The Water vapor transmitted, which is expressed in grams per hour per square meter. is corrected for variations in temperature and humidity by running a control with a standard balloon cloth (Sak or pima cotton, 2.0: 0.1 oz./yd. warp count 133, fill count 134, plain weave) and multiplying the measured moisture vapor transmission of the test sample by 47.5, the average moisture vapor transmission of the standard cloth, and dividing by the control measurement of the standard cloth. This method of testinggives accurate reproducible test data.

Conventional fabrics water-proofed by rubber coatings usually have moisture vapor transmissions of less than 5 grams per hour per square meter, while fabrics prepared in accordance with this invention will have moisture vapor transmissions in excess of 15 grams per hour per square meter and preferably in excess of 20 grams per hour per square meter.

The hydrostatic head of a film or fabric is the pressure, usually measured in height of water, which is required to force water through the film or fabric. The hydrostatic head may be measured by the method, ASTM D583-40T, procedure B, section 6. Water-proof fabrics should have hydrostatic heads of over 125 cm. of water and preferably over 200 cm. of water, whereas the hydrostatic heads of water-repellent fabrics do not exceed '15 cm. of water. Although fabrics have been prepared with hydrostatic heads within the above defined preferred range, it has been accomplished by sacrifice of the moisture vapor transmission rate. Similarly fabrics of the desired moisture vapor transmission rates have been prepared but only by giving up the desirable resistance to liquid water under pressure. This invention makes it possible to achieve both of the desired properties to an effective extent.

Further details of the preparation of the coating compositions and the laminated fabrics prepared therefrom are set forth with respect to the following specific examples.

Example 1 A polychloroprene latex containing approximately 50 percent rubber solids (Neoprene 5'71) was mixed with the following materials, the quantities being based on 100 parts by weight of the polychloroprene:

Casein 5 Water glass 15 Calcium carbonate 25 Zincoxide 25 Hexamethylene tetramine 3 Agerite white 3 Methyl cellulose 3 1 Antioxidant amine.

sym. dibetanaphthyl-p-phenylene di- The casein was added as a 10 percent water solution of ammonium caseinate and the water glass was also added in water solution. The materials were mixed by means of high speed propeller type agitators, and, when thoroughly mixed, parts of water were added. One hundred parts by weight .(3.5 volumes). of diatomaceous silica were then thoroughly mixed into the latex.

The latex paste so prepared was spread on cotton sheeting weighing 3.6 oz./ sq. yd. and having 58 threads per inch in the warp and 50 threads in the fill. The fabric was coated with three layers of the material with the spreading knife set at 0.0010.002 inch. Each layer was dried thoroughly over steam coils before applying the next layer. The coated fabric was cured in an oven for 50 minutes at 105 C. The resulting product was measured to determine its moisture vapor transmission which was found to be 22 grams/hn/mfi. The hydrostatic head was measured and found to be 200 cm. of water.

Example 2 A polychloroprene rubber (GR-M) was milled on a laboratory-size rubber mill with the following materials; the parts being by weight based on 100 parts of polychloroprene:

Zince oxide Calcined magnesia 10 Phenylbetanaphthylamine 2 Sulfur 2 The compounded rubber was placed in a dough mixer and thinned by 762 parts by weight of toluene. After mixing to a thin uniform cement 112 parts by weight (4 volumes) of diatomaceous silica were added.

After this, the cement was spread on a cloth fabric identical to that used in the preceding example by coating once with the doctor blades and thereafter with three coats each 0.001 to 0.002 inch in thickness. The coated fabric was then dried in hot air to evaporate the excess toluene and cured for 60 minutes at 280 F. The hydrostatic head was found to be 287 cm. of water and the moisture vapor transmission was found to be 35 grams/hn/mfi.

The method of this invention may be used to coat cloth utilizing other resins or rubbers containing high proportions of hydrophilic diatomaceous silica. Preferably in excess of three volumes of the pigment are used per volume of the rubber or resin. Thus, the following rubbers and resins may also be used: synthetic rubber including copolymers of hydrocarbondienes and 20 to 50 percent of other mono-olefinic monomers, such as styrene, acrylonitrile or the acrylates; natural rubber, including hevea and other vulcanizable natural resins; vinyl chloride resins, including polyvinyl chloride and copolymers of vinyl chloride and from 5 to 20 percent of vinyl acetate, ethyl fumarate, or the alkyl acrylates and methacrylates; the polyvinyl acetals, including polyvinyl butyral; polyvinyl alcohol; polymers of aliphatic mono-olefinic compounds including polyisobutylene and butyl rubber; linear polyamide interpolymers, including the soluble nylons; the polymerized alkyl acrylates, including polymethyl methacrylate, polymethyl chloroacrylate and polymethyl acrylate.

Although the invention has been described with respect to specific examples it is not intended that the details thereof shall be construed as limitations on the scope of the invention except to the extent incorporated in the following claims.

I claim:

1. A water-impervious and water vapor-permeable fabric which comprises a woven textile fabric coated with a continuous layer of rubberlike polychloroprene, said polymer containing intimately dispersed therein from two to six volumes, based on the polymer, of a hydrophilic diatomaceous earth.

2. A water-impervious and water vapor-permeable fabric which comprises a woven textile fabric coated with a continuous layer of rubberlike polychloroprene, said polymer containing intimately dispersed therein from three to five volumes, based on the polymer, of a hydrophilic diatomaceous earth.

3. A method of preparing a water-impervious and water vapor-permeable coated fabric which comprises mixing a latex of a rubberlike selfpolymer of 2-chlorobutadiene1,3 with from three to five volumes, based on the polymer, of a hydrophilic diatomaceous earth, and applying a continuous layer of said polymer on a woven textile fabric by spreading the mixture on the fabric, drying the coating by evaporation of the water in the latex, and vuloanizing the coating.

4. A method of preparing a water-impervious and water vapor-permeable coated fabric which comprises mixing an organic solvent dispersion of a rubberlike self-polymer of 2-chlorobutadiene-1,3 with three to five volumes, based on the polymer, of a hydrophilic diatomaceous earth, and applying a continuous layer of said polymer on a woven textile fabric by spreading the mixture on the fabric, drying the coating by evaporation of the organic solvent, and vulcanizing the coating.

DAVID N. BEAUCHAMP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Dec. 28, 1933 Certificate of (Jorrection Patent No. 2,575,577 November 20, 1951 DAVID N. BEAUCHAMP It, is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 55, for photophyta read protophyta; column 3, line 7, strike out the comma after the syllable ene;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 4th day of March, A. D. 1952.

THOMAS F. MURPHY,

Assistant Commissioner of Patenta. 

1. A WATER-IMPERVIOUS AND WATER VAPOR-PERMEABLE FABRIC WHICH COMPRISES A WOVEN TEXTILE FABRIC COATED WITH A CONTINUOUS LAYER OF RUBBERLIKE POLYCHLOROPRENE, SAID POLYMER CONTAINING INTIMATELY DISPERSED THEREIN FROM TWO SIX VOLUMES, BASED ON THE POLYMER, OF A HYDROPHIC DIATOMACEOUS EARTH 